bzsz1942 wrote:If BL 5 is not recommended for the cub tranny, where can you find BL4?

Do you mean GL-4 & GL-5? These gear oils contain extreme pressure additives that are corrosive to yellow metals. Like Eugene suggested you should use Hy-Tran. Another option is GL-1, which is a straight mineral oil and compatible with yellow metals. But, good luck on finding any GL-1.......pretty scarce these days.

This may be a stupid question, but I don't know. What do you mean by yellow metals? I have been using Mystic HP 90 wt in my Cub tranny for several years. My Son-in-law has a brother who races around here, nd he said a lot of the racers use the Mystic oil in their differentials, and it eliminated troubles they used to have.

That may explain why the reverse idler bushing is almost always worn in the old cubs that did not use Hy Tran.And why they are so noisy. Another good reason to use Hy Tran . And the Idea of using thicker oil in the trany to keep noise down, well you may as well put saw dust in it too . Thats what the car dealers use to do Boss